In modern vehicle information systems, the driver of a motor vehicle can be given information about the current state of the roadway, in particular in the case of a wet roadway, a snow-covered or a frozen over roadway. In order to ensure that information about the roadway state is made available in a reliable manner, the evaluation of measurement signals of one sensor or more sensors is usually required. This data is evaluated in the case of anti-lock brake systems (ABS) or anti-slip traction control systems (ASR) in order to obtain reports about the state of the roadway. It is then possible by interventions in different components of the motor vehicle to exert an influence on the driving behavior of the motor vehicle.
DE 10 2004 016 288 B3 discloses a method for determining a friction value in the case of which the vibrations of a tire are detected and one characteristic of the tire vibration, in particular a frequency spectrum and/or a time domain spectrum is evaluated. To this end, the following steps are carried out: Data is evaluated by means of physical and/or phenomenological model approaches, evaluation signals are observed in at least two frequency bands, amplitudes of the evaluation signals are compared with friction value-dependent empirical values also dependent on a current force transfer condition of the tire, a friction value is derived and from the friction value a maximum available force that can be transferred from the tires to the roadway is determined.
The publication “Estimation of Tire-Road Friction by Tire Rotational Vibration Model” (Takaji Umeno, R&D Review of Toyota CCRDL, vol. 37 No. 3) discloses a method for the estimation of a friction value between the roadway and the tires for a free-rolling wheel in the case of which a frequency analysis of the angular speed of the wheel of the vehicle is used.